1. Field of the Invention
This invention relates to an improved assembly of a pneumatic tire and a wheel rim, and has as its particular object to provide an assembly which is free of the disadvantage in which the bead areas separate from the bead seat of the rim both when the inner air pressure of the tire is decreased and when the tire is punctured and which also has good safety and durability.
2. Description of the Prior Art
Pneumatic tires (hereinafter simply referred to as "tires" in this specification), for example, passenger car tires, have ordinarily an inner air pressure of about 1.5 to 2.0 kg/cm.sup.2. When the car is running under a condition of a reduced inner air pressure of the tire of 0.5 to 1.0 kg/cm.sup.2 and the vehicle makes a sudden and rapid turn, the bead areas of the tire tend to separate from the bead seat of the rim, which leads to not only a failure of the tire, but also to an unstable running of the vehicle and as a result, the running vehicle becomes dangerous.
Particularly when the tire is punctured, whether the running vehicle is suddenly and rapidly turned or is driven straight, the tire separates from the rim and control of the vehicle is lost. As a consequence, an accident which can cause death and injury often happens. When the tire separates from the rim, the vehicle runs with the rim in contact with the road surface, ultimately, so that the rim and road surface are damaged and the tire breaks down while the driving of the vehicle becomes extremely unstable. Thus, tragic traffic accidents result.
In view of these circumstances, various safety tires have been heretofore proposed which exhibit high safety preformance when the inner air pressure of the tires is reduced or the tires are punctured, that is to say, when the tires are in a so-called "run flat" condition. Examples of these safety tires include (1) a tire in which a spacer is interposed between a pair of beads facing one another, thereby fixing the bead areas so that the bead areas do not separate from the bead seat of a rim; (2) a tire in which plurality of air chambers are formed by inserting an inner tire inside an outer tire; (3) a structure in which a tire is mounted on a rim, and a bolt is set on the rim to prevent separation of the bead areas from the rim; and others.
The tires or structures as proposed above, however, have not yet been widely used in practice because of the following numerous drawbacks:
Namely, in the tire as described in (1) above, in which a spacer is interposed between a pair of beads, the cost of the tire is increased since the spacer interposed between the beads comprises a metal or a rubber and fiber and further, when the tire is practically mounted on a rim many difficulties are encountered. On the other hand, in the tire as described in (2) above, in which a plurality of air chambers are formed by inserting an inner tire inside an outer tire, the manufacture of the inner tire to be inserted inside the outer tire requires almost the same processing stages as those of manufacture of the outer tire, the resulting structure is naturally complicated and an air valve for the multi-chambered tire must also be employed, which leads to increases in costs. These tires have not been practically and widely used due to the restrictions above. Further, the tire as described in (3) above, in which a tire mounted on a rim and bolted, problems in respect to safety and durability of the rim still persist since the rim is set with a bolt.
In addition to the tires described above, an assembly of a tire and a rim has also been proposed in which the bead areas of the tire and the rim are integrally united, but this assembly also has drawbacks in that the usual methods for manufacture of tires and usual specifications with respect to the rim must be changed greatly and it is impossible to mount and demount the tire, e.g., for changing the tire.
Thus, it can be seen that although various improvements have been proposed hitherto, many obstacles exist in these prior proposed constructions from a practical viewpoint.